Study Finds Fish Assemblages in Replanted Mangrove Areas Closely Resemble Those in Natural Forests
New Delhi, September 23. (SDNA) — A long-term mangrove restoration effort in Guyana has produced encouraging ecological results, with a scientific study finding that restored mangrove forests can support fish communities comparable to those found in naturally established mangrove habitats.
The study examined mangrove sites restored along Guyana’s coast several years after more than half a million mangrove seedlings were planted. Researchers found no significant difference in fish abundance or community composition between restored and natural mangrove areas, suggesting that rehabilitated coastal habitats can become functional fish habitats within a relatively short period.
Restoration Programme Began in 2010
Guyana’s mangrove ecosystems have experienced significant pressure over the years from coastal erosion, deforestation, sediment accumulation and pollution. Available estimates cited in the study indicate that the country’s mangrove coverage declined sharply, from around 150,000 hectares in 1983 to approximately 81,000 hectares in 1992 and about 22,000 hectares by 2011.
Against this backdrop, Guyana launched a large-scale mangrove restoration programme in 2010. More than 500,000 mangrove seedlings were planted across 19 sites covering an approximately eight-kilometre stretch of coastline.
The restoration primarily involved Avicennia germinans, commonly known as black mangrove, with the objective of rebuilding vegetation and strengthening the ecological functions of degraded coastal areas.
Natural and Restored Mangroves Put Under Comparison
For the research, scientists selected 10 mangrove sites—five restored locations and five naturally established areas. Restored forests ranging from five to 11 years in age were examined alongside natural mangrove habitats to assess how closely their fish communities had developed.
The natural sites had emerged under favourable coastal conditions following the stabilisation of mudflats and included black, white and red mangrove species.
Satellite imagery was also used to help establish the age and development history of the natural mangrove areas. Fish sampling was conducted across different seasons and during both daytime and nighttime periods to obtain a broader picture of the aquatic communities using the habitats.
559 Fish Representing 18 Species Recorded
Researchers recorded 559 individual fish belonging to 14 families and 18 species during the survey. Each site was assessed for fish abundance, species composition and biological characteristics such as length and weight.
One of the study’s key findings was that there was no statistically significant difference in fish abundance between restored and natural mangrove sites. The researchers also found no clear direct relationship between the age of a restored mangrove site and the number of fish recorded there.
Five species accounted for approximately 94 per cent of all fish captured. Sciades couma was the most frequently recorded species, followed by Anableps anableps, Sciades herzbergii, Amphiarius rugispinis and Colomesus psittacus.
Fish Quickly Began Using Restored Habitats
The research indicated that restored mangrove areas were able to attract a large proportion of the fish species associated with natural mangrove ecosystems.
Approximately 90 per cent of the fish species recorded in natural mangroves were also found in the restored areas, indicating that newly established mangrove habitats can begin providing aquatic habitat relatively early in their development.
Interestingly, the oldest restored forest did not necessarily contain the highest number of fish. A six-year-old restored site accounted for about 40 per cent of the overall fish community recorded in the study, compared with roughly 26 per cent at a five-year-old site and 19.5 per cent at an 11-year-old site.
The findings suggest that factors beyond the age of a mangrove forest—including local environmental conditions and habitat characteristics—can influence how fish use restored areas.
Vegetation Continued to Develop Over Time
The researchers also documented substantial vegetation growth in the restored forests. Species including Avicennia germinans, Laguncularia racemosa and Rhizophora mangle were recorded across the study sites.
A total of 894 trees were counted in the restored areas, compared with 446 trees in the natural sites. However, the natural mangroves had a higher density of Rhizophora mangle.
Natural mangrove trees were also slightly taller on average. Their mean height was recorded at approximately 12.52 metres, compared with around 11 metres in the restored areas. Differences were also observed in average trunk diameter.
Restoration Goes Beyond Planting Trees
The findings highlight an important aspect of ecological restoration: successful mangrove recovery cannot be measured simply by counting the number of trees planted.
The study indicates that when suitable coastal conditions are present, restored mangrove forests can become valuable habitats for fish within a relatively limited period. Although differences remained between natural and restored forests in terms of vegetation structure, the fish communities showed considerable similarity.
The Guyana experience therefore provides useful scientific evidence for coastal restoration programmes seeking to rebuild mangrove ecosystems and recover their role as fish habitats.
Mangroves are widely recognised for their ecological functions, including providing shelter and feeding grounds for aquatic species, stabilising coastlines and supporting coastal biodiversity. The findings from Guyana suggest that carefully planned restoration can help recover some of these functions even before a restored forest fully develops the structural characteristics of a mature natural mangrove ecosystem.
— SDNA